In the past, numerous methods and devices have been used to securely hold a threaded object such as a bolt, stud, or threaded rod when the object is to be worked on for any of a number of reasons. One approach has been to insert wooden boards along the sides of a vise and then clamp the threaded object between the boards to prevent damage to the threads. This arrangement has been cumbersome, has not always prevented damage to the threads, and has not been susceptible of applying sufficient force to the threaded object under all circumstances.
Another approach common in the art of stud removal has been to double nut a threaded object to turn it. One nut of suitable size is run onto the threaded object, and a second nut is run up against the first. The second nut is tightened against the first nut, thus binding the two nuts on the threaded object for the purpose of rotating the threaded member by applying force to one nut or the other depending on the direction of rotation desired. This arrangement also has met with difficulties in that it applies a great amount of stress on the threads and often results in one of the two nuts becoming loosened and defeating the purpose of the arrangement.
Certain other approaches have been used in connection with devices in this general field. Valvano Pat. Nos. 2,571,968 and 2,681,582 disclose multi-piece arrangements for securing a threaded member. The '968 patent includes a threaded bore and a wedge-shaped locking member, and the '582 patent discloses a two-piece arrangement including a pair of jaws which are biased apart from each other, but which may be closed to apply pressure to the threaded object. These devices may be operable for insertion of studs or removal of studs which are clean, but cannot provide sufficient gripping pressure for removal of studs which have rusted in place.
Typical of prior art die cutting arrangements are the devices shown in U.S. Pat. Nos. 451,890, 1,048,921, 1,416,059, and 2,054,745. Campaigne U.S. Pat. No. 1,857,493 shows a thread-chasing device including opposed clamp blocks with a polygonal opening and a cutting member designed to engage the angle of the threads to be operated on. U.S. Pat. No. 1,897,666 deals with a multi-part machine tool spindle. U.S. Pat. No. 3,094,022 discloses a threaded stud extractor tool utilizing rows of circumferentially spaced, longitudinally spaced set screws for engaging a stud and applies torque thereto.
It will be seen that the prior art discussed comprises relatively complex and expensive arrangements which are capable of exerting only limited gripping force as opposed to the unitary, one-piece, simple design of the invention herein which is capable of applying substantial gripping force when required.